|  | 2.3 | Switching and VLANs
| 2.3.5 | How a switch learns addresses
An Ethernet switch can learn the address of each device on the network by reading the source address of each packet transmitted and noting the port where the frame entered the switch. The switch then adds this information to its forwarding database. Addresses are learned dynamically. This means that as new addresses are read, they are learned and stored in content-addressable memory (CAM). When a source is read that is not found in CAM, it is learned and stored for future use. Each time an address is stored, it is time stamped. This allows for addresses to be stored for a set period of time. Each time an address is referenced or found in CAM, it receives a new time stamp. Addresses that are not referenced during a set period of time are removed from the list. By removing aged or old addresses, CAM maintains an accurate and functional forwarding database.